Optical modulation system

Abstract

A system comprises a substrate 4, an incident optical waveguide 5 formed on the substrate for receiving a light beam incident thereto, two phase-shift optical waveguides 6 formed on the substrate 4 to be branched from the incident optical waveguide 4 for varying a phase of a transmitted light beam in response to an electric field intensity, an outgoing optical waveguide 7 formed on the substrate 4 to join the phase-shift optical waveguides 6. At least one of the phase-shift optical waveguides 6 has a reversely polarized portion 8 reversely polarized. A light transmission film may be formed at one or a plurality of portions on the phase-shift optical waveguides 6. A buffer layer 14 may be formed on a part on or in the vicinity of the phase-shift optical waveguides 6. A transparent substance film for imparting a stress to one of the phase-shift optical waveguides 6 may be formed on a part or a whole of a portion without the buffer layer 14. A stress imparting member may be formed to impart a stress to a part of one of the phase-shift optical waveguides 6. A light irradiation unit 26 may be formed to irradiate a light beam onto a part or a whole of one of the phase-shift optical waveguides 6.

We claim: 
     
       1. An optical modulation system comprising: a substrate;   an incident optical waveguide formed on said substrate for receiving a light beam incident thereto;   two phase-shift optical waveguides formed on said substrate and being branched from said incident optical waveguide for varying a phase of a transmitted light beam in response to an electric field intensity;   an outgoing optical waveguide formed on said substrate and joined to said two phase-shift optical waveguides; and   a light transmission film formed at one or a plurality of portions on one of said two phase-shift optical waveguides.   
     
     
       2. The optical modulation system of claim 1, wherein said light transmission film comprises an SiO 2  film and is formed by a sputtering process. 
     
     
       3. The optical modulation system of claim 2, further comprising two modulation electrodes formed on said substrate and located in the vicinity of said two phase-shift optical waveguides. 
     
     
       4. The optical modulation system of claim 1, wherein said light transmission film is an SiO 2  film. 
     
     
       5. The optical modulation system of claim 1, further comprising two modulation electrodes formed on said substrate and located in the vicinity of said two phase-shift optical waveguides. 
     
     
       6. The optical modulation system of claim 1, further comprising two modulation electrodes formed on said substrate and located in the vicinity of said two phase-shift optical waveguides.